In a cellular mobile communication system, in order to enlarge coverage of a cell and/or in order to realize load distribution in a base station (eNB), there is a case where a relay station (relay node: RN) is provided between the base station (eNB) and a mobile station (more generally, user apparatus (UE)). The base station (eNB) in this case functions as a parent station, and may be referred to as a donor base station (donor eNodeB: DeNB). Although the user apparatus (UE) is a mobile station typically, it may be a fixed station. The user apparatus (UE) may be any proper apparatus such as a mobile phone, an information terminal, a smart phone, a personal digital assistant, and a mobile personal computer. A radio interface between the base station (eNB) and the relay station (RN) is referred to as “Un”. A radio interface between the relay station (RN) and the mobile station (UE) is referred to as “RN-Un”.
In order to perform radio communication with the base station (eNB), it is necessary to properly establish a radio bearer or a logical path after it becomes possible to access the base station (eNB) by receiving a notification signal from the base station (eNB). That is, it is necessary to adapt various parameters in each sublayer such as RLC, MAC, and PDCP sublayer to the base station (eNB). Setting of the logical path needs to be carried out not only by the user apparatus (UE) but also by the relay station (RN). In this case, setting of the logical path of the user apparatus (UE) and setting of the logical path of the relay station (RN) are different at least partially.
For example, the relay station (RN) uses the time division duplex (TDD) scheme in order to realize reception from the base station (eNB) and transmission to the user apparatus (UE) by half duplex scheme using the same frequency. In this case, it is necessary that the relay station (RN) receives a signal from the base station (eNB) by using a subframe that can be configured to transmit MBSFN (Multimedia Broadcast multicast service Single Frequency Network). On the other hand, there is no such restriction for the user apparatus (UE). Therefore, setting of the logical channel is different between the relay station (RN) and the user apparatus (UE) at least with respect to usage of the subframe. Other than the setting of the subframe, there is a possibility that there are differences in settings of information indicating usage of resources in semi-persistent scheduling (SPS), information indicating resources of a sounding reference signal (SRS), and configuration information in MAC sublayer, for example.
Therefore, it is necessary that the base station (eNB) provides information for establishing (setting) the logical path for the relay station (RN) and the user apparatus (UE). According to a 3GPP standard specification discussed before filing the present application, it is studied that the base station (eNB) transmits an individual RRC message including setting information common to the user apparatus (UE) and the relay station (RN), and an individual RRC message including setting information dedicated to the relay station (RN) (for this technique, please refer to non-patent document 1, for example).